Powertrain systems are equipped with on-board sensors that monitor powertrain operating parameters for purposes of control and diagnostics. Such sensors include devices for monitoring fluidic temperature, rotational position and speed, airflow, and others. Sensors may be monitored to verify sensor performance and integrity. Such monitoring may include evaluating signal continuity, e.g., detecting occurrence of electric grounding of an output signal or detecting occurrence of an open circuit associated with the output signal. There may be a further need to monitor sensor signal rationality to verify in-use that an output signal from a sensor is responsive to the operating parameter the sensor is monitoring.